Ceramide-1-phosphate (C1P), the product of ceramide kinase, is a sphingophospholipid with recently recognized important signaling properties. In particular, it was reported to have mitogenic activity, and to be capable of direct stimulation of cytosolic phospholipase A (2α). C1P has been observed to be able to stimulate cell division, induce DNA synthesis, block apoptosis and promote cell survival. It has been recognized as one of the most important mediators that affect the physiology of cells, and has caused much interest in using it as a potential therapeutic agent.
Accordingly, there is currently much research into the properties and use of C1P. However, delivering C1P intracellularly, the actual loci of its action, is not trivial. Previous research into C1P has relied on the use of C1P of various acyl chain lengths and diverse protocols to deliver it to cultured cells. Typically, intracellular delivery of C1P was achieved by adding the lipid in a mixture of alcohol/dodecane. Most commonly, a mixture of ethanol or methanol with dodecane is used as the vehicle.
However, it has been reported that the inclusion of dodecane in this method induces artifacts in the cells, thereby rendering many observed effects of C1P unreliable. See, for example, Gómez-Muñoz et al., FEBS Letters 579, 3744-3750 (2005).
Another method that has been employed to introduce C1P into the cytosol is to produce C1P in situ by transfecting cells with ceramide kinase, the enzyme that catalyzes the phosphorylation of ceramide. However, many cells cannot be transfected (such as primary bone marrow-derived macrophages).
The difficulty in delivering C1P to intracellular compartments has contributed to the lack of progress with this important molecule both as a research target and as a therapeutic agent. As a result, much of C1P signaling is still poorly understood.
Although these problems were acknowledged at least as early as 2005, see above, a solution has heretofore not been found.